Process for removing tin from tin-plate waste.



, UNITED STATES PATENT OFFICE.

. HEIN' RICH BRANDENBURG, OF KEMPEN-ONTHE-IR.HINE, GERMANY.

PROCESS FOR REMOVING TIN FROM TIN-PLATE WASTE.

Specification of Letters Patent.

Patented Nov. 1, 1910.

No Drawing. Original application filed March 3, 1908, Serial No. 418,933. Divided and this application filed August 11, 1908. Serial No. 448,062.

To all whom it may concern:

Be it known that I, HEINRICH BRANDEN- BURG, a subject of the King of Prussia, residing and having a post-oflice address. at

29. Moorenring, Kempen-on'the-Rhine', Ger

many, have invented a new and useful Improvement in Processes for ,Removing Tin from Tin-Plate \Vaste and other Tin-Containing Material; and I 'do hereby declare the following to be a full, clear, and exact description of the same.

The present application is a division of an.

application-Sci. No. 418933, filed 3rd March 1908, for Letters Patent of the United States.

It is well known that tin-plate-waste' can be deprived of tin by exposing it to the .action of hot caustic alkaline lye, such for instance as solutions of caustic soda and air. In that process the tin is oxidized into oxid of tin, or stannic acid which passes into solution in the shape of stannates of alkalies for .instance, stannate of soda. This wellknown process is, however, combined with difliculties which are removed by the process according to this invention.-

As it is known, the alkaline lye combines in such process on one hand with the carbonic aoid of the air forming thus carbonate of soda, and on the other hand with the oxidized tin forming stannate of soda. and consequently loses shortly afterward its capacity of dissolving tin. Besides the thus formed stannate of soda separates from the solution and settles on the tin-plate-waste to be treated andprcvents the tin from dissolving, hindcring the contact between the alkaline lye and the tinned surface of the plate-waste. This inconvenience 1s dispensed with according to the present lIlVCl'ltion b contlnuousl Y or at certain intervals renewing the alkaline lye by supplying fresh caustic alkaline lye and.by discharging corstannates and car onates, and supplies in; 13 181: place cor esponding quantities of fresh-talkaline lye. In first instance this process is intended to be used in connection with the a paratus described in my U.,'S.

patent app ication Ser. No. 418933 filed 3rd March 1908.

I claim:

The process of removing tin from tin plate, scrap or other tin containing ma- 'terial, together with thesimultaneous pro duction of oxid of tin, which consists 1n flowing a solutlon of caustic alkali over the tin contamlng materlal, air/being present 1n said solution in such quantity as to insure the formation of an 'oxygencolnpound of tin, the caustic alkali thereafter converting said compound into stannic alkali with the additional formation of an alkaline carbonate in the fluid mass, removing in part that portion of said alkaline solution encumbered with alkaline carbonate and stannic alkali leaving the principal part of the solution still active, to facilitate the continued formation of said oxygen compound of tin, and continuously supplying fresh quantities of the aerated alkaline reagent to effect a continuous and substantially uniform production of said stannic alkali, sub stantiully as described.

In testimony whereof I have signed my certain quantities" of name to this specification in the presence of two subscribing witnesses.

HEINRICH BRANDENBURG. \VIhICSSES O'i'ro Kiimc, WM. WAsmNo'roN BRUNSWICK. 

